An increase in integration density of an integrated circuit semiconductor device (semiconductor chip) is drastically decreasing the design rule in order to integrate more transistors in a limited substrate area. As a result, an area and length of a transistor in a cell area (hereinafter, referred to as a cell array transistor) of the integrated semiconductor device such as a dynamic random access memory (DRAM) device are greatly decreasing.
The decrease in the design rule of the integrated circuit semiconductor device results in a short-channel effect and deterioration of current driving capability of the cell array transistor. It is necessary to overcome such limitations of the cell array transistor of the integrated circuit semiconductor device. Also, a peripheral circuit region is required to drive the cell array transistor of the integrated circuit semiconductor device. Examples of the peripheral circuit region may include a sense amplifier region, a word line driver region and a support circuit region. A peripheral circuit transistor is formed in the peripheral circuit region. The peripheral circuit transistor also needs to have improved integration density because of the decrease of the design rule in the integrated circuit semiconductor device.
When the cell array transistor or the peripheral circuit transistor is implemented on a substrate, there is a need to fabricate the integrated circuit semiconductor device with improved integration density through a simple process.